1. Field of the Invention
The present invention relates to an automatic switchover device for a power source, designed to automatically switch over systems for supplying electric power to an electric load in such a manner that electric power output from an engine generator is supplied to the electric load upon occurrence of the power failure of a regular power source system.
2. Description of the Related Art
There is an automatic switchover device known, for example, from Japanese Patent Application Laid-open No.5-64382 and the like, which is designed so that a switch is changed over to supply electric power output from an engine generator to an electric load upon occurrence of the power failure of a regular power source system.
In such an automatic switchover device for the power source, it is necessary not only to provide an emergency automatic switchover mechanism, but also to provide a measure for enabling switching by an operator""s manual operation in case of failure or the liked of a control unit. It is general that a special switching lever structure or the like is mounted on the conventional automatic switchover device.
The present invention has been achieved with the above circumstances in view, and it is an object of the present invention to provide an automatic switchover device for a power source, wherein the switching can be achieved by the operator""s manual operation without provision of a special mechanism.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an automatic switchover device for a power source, comprising: a switching unit which has first and second individual contacts individually leading to a regular power source system and an engine generator, and a common contact leading to an electric load, wherein the common contact can be alternatively electrically connected to the first and second individual contacts; and a control unit for controlling the switching unit in such a manner that the common contact is electrically connected to the second individual contact in response to the regular power source system being electrically failed, and the common contact is electrically connected to the first individual contact in response to the restoration of the regular power source system, wherein the switching unit includes: a seesaw-type turn member carried on a support frame for turning movement between a first turned position in which the turn member permits the common contact to be electrically connected to the first individual contact and a second turned position in which the turn member permits the common contact to be electrically connected to the second individual contact, a spring member for exerting a spring force for retaining the turn member in one of the first and second turned positions in response to the turning movement of the turn member passing through a central point between the first and second turned positions toward one of the first and second turned positions, a first solenoid capable of exerting an electromagnetic force for driving the turn member toward the first turned position against the spring force of the spring member, and a second solenoid capable of exerting an electromagnetic force for driving the turn member toward the second turned position against the spring force of the spring member, the first and second solenoids each including a plunger which integrally comprises an operating portion enabling the plunger to be pushed in from the outside.
With such arrangement of the first feature, the supplying of the electric power from the engine generator to the electric load upon the occurrence of the power failure of the regular power source system and the supplying of the electric power from the regular power source system to the electric load upon the restoration of the regular power source system can be automatically switched over from one to the other by controlling the energization and de-energization of the first and second solenoids in a switching manner by the control unit. Moreover, in case of emergency, the electric connection between the regular power source system and the electric load and the electric connection between the engine generator and the electric load can be alternatively switched over from one to the other by pushing in the operating portions integrally provided on the plungers included in the solenoids, without utilizing the energization or de-energization of the first and second solenoids. Furthermore, it is unnecessary to mount a special lever mechanism or the like, and it is possible to achieve the switching operation by an operator""s manual operation in a simple structure in which the operating portions are merely integrally provided on the plungers.
According to a second aspect and feature of the present invention, in addition to the arrangement of the first feature, the common contact is provided on a movable contact-supporting member which is operably connected to the turn member for turning movement about an axis coaxial with the turn member, and the switching unit is accommodated in a box body having an opening capable of being opened and closed by a lid member in such a manner that the operating portions are disposed on the side of the opening, and the turn member and the movable contact-supporting member are disposed on the side opposite from the opening. With such arrangement, contact portions of the first and second contacts and the common contact are disposed inside the box body, whereby the contact with the contact portions from the outside can be prevented to the utmost and moreover, the operator""s manual operation can be facilitated by the disposition of the operating portions on the side of the opening.
According to a third aspect and feature of the present invention, in addition to the second feature, the common contact is provided at each of opposite ends of the movable contact-supporting member; the first and second individual contacts capable of being electrically connected to the common contact are fixedly disposed at locations corresponding to the opposite ends of the movable contact-supporting member; first and second power source terminal members individually connected to the regular power source system and the engine generator are connected to the first and second individual contacts; and a load terminal member leading to the electric load and fixedly disposed at a location corresponding to a central portion of the movable contact-supporting member is connected to the common contact. With such arrangement, the first and second power source terminal members are fixedly disposed at the opposite ends of the movable contact-supporting member, and the load terminal member is fixedly disposed in correspondence to the central portion of the movable contact-supporting member. Therefore, electric cords leading to the first and second power source terminal members and the load terminal member can be easily arranged in such a manner that a wiring line is distributed for each of the electric cords.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.